The manuscript has been organized so that the confirmation tests, such as FTIR, XRD, EDX, SEM, and TGA, are discussed. Second, functional properties such as water and oil repellent, oil-water separation, acid resistance self-cleaning, flame retardant, UV protection and antibacterial have been addressed. Physical and mechanical properties have been addressed in the third section. Fourth, thermal conductivity, air permeability, and water vapor permeability have all been explored as comfort properties. Finally, the comfort data were analyzed statistically. Each result will be analyzed and discussed below.
FTIR spectra
In Fig. 4a, FTIR spectra of scoured bleached cotton show a broad peak at 3331 cm−1 signifying the OH stretching vibration of cellulose hydroxyl groups in the region of 3100-3600 cm−1. The scoured bleached cotton fabric spectra also showed typical characteristic peaks at 1428 cm−1and 2900 cm−1, which may be C-H bending and stretching bands, respectively. (Chung et al. 2004). Wavenumber 3331 cm−1 of bleached cotton fabric has been converted into little high wave numbers of FC-dendrimer treated cotton fabrics as shown in Fig. 4 (b, c, d, e, f), which indicated intermolecular hydrogen bond formation. The peak at 2900 cm−1 of bleached cotton fabric has been shifted to a little lower wavenumber of the FC-dendrimer-treated fabrics except for 60 g/L. A peak at 1427 cm−1 has also changed after FC-dendrimer treatment. These changes prove that FC-dendrimer was successfully attached to the cotton fabric.
XRD Analysis
Table 2
Measurement of crystallinity percentage (Cr %) of untreated and FC-dendrimer treated fabrics.
Observation
|
2 theta (\(^\circ )\)
in the CR
|
Intensity in counts
|
2 theta (\(^\circ )\)
in the AR
|
Intensity in counts
|
Cr%
|
60 g/L FC-dendrimer
|
22.56
|
2333
|
18
|
433
|
81.44
|
70 g/L FC-dendrimer
|
22.60
|
2413
|
18
|
483
|
79.98
|
80 g/L FC-dendrimer
|
22.43
|
2246
|
18
|
432
|
80.76
|
90 g/L FC-dendrimer
|
22.46
|
2028
|
18
|
409
|
79.83
|
100 g/L FC-dendrimer
|
22.44
|
2166
|
18
|
478
|
77.93
|
Untreated fabric
|
22.51
|
2519
|
18
|
448
|
82.21
|
N.B: Crystalline Region (CR), Amorphous Region (AR) |
Table 3
Measurement of crystal diameter and inter plane spacing (d) of untreated and FC-dendrimer treated fabrics.
Observation
|
2 theta (\(^\circ )\)
in the CR
|
Inter plane spacing
‘d’ in nm
|
FWHM
(\(^\circ )\)
|
Crystal diameter (nm)
|
60 g/L FC-dendrimer treated
|
22.56
|
0.393806
|
1.406
|
5.77
|
70 g/L FC-dendrimer treated
|
22.60
|
0.393118
|
1.497
|
5.44
|
80 g/L FC-dendrimer treated
|
22.43
|
0.396059
|
1.616
|
5.04
|
90 g/L FC-dendrimer treated
|
22.46
|
0.395536
|
1.561
|
5.17
|
100 g/L FC-dendrimer treated
|
22.44
|
0.395884
|
1.688
|
4.89
|
Untreated fabric
|
22.51
|
0.394669
|
1.375
|
5.84
|
* FWHM- Full width at half maximum |
The untreated and FC-dendrimer-treated fabrics both showed three distinctive peaks, at the crystal planes of (101), (002) and (040) as shown in Fig. 5. This result agrees with the result found by Altınışık et al., (Altınışık et al. 2013) for cellulosic fibre. The crystallinity percentages of 60g/L, 70g/L, 80g/L, 90g/L, and 100g/L FC-dendrimer-treated samples were 81.44, 79.98, 80.76, 79.83, and 77.93%, respectively (Table 2). The crystallinity percentage of the treated samples slightly decreased compared to those of the untreated samples (82.21%), the peak intensity of the treated fabric also decreased when 2\(\theta\) value at the crystal plane was (002). The crystallinity percentage of the FC-dendrimer-treated samples gradually decreased as the FC concentration increased. As a result, the FC-dendrimer-treated fabric exhibited a slightly lower level of crystallinity. On the other hand, the full width at half maximum (FWHM) value of the FC-dendrimer-treated sample was greater than that of the untreated sample.
The full width at half maximum (FWHM) value is inversely proportional to the crystal diameter. Full length at half maximum value increases, the crystal diameter of the sample decreases according to Deby-Scherrer formula (Eq. no. 2. Thus, the crystal diameter of all FC-dendrimer-treated cotton fabrics was lower than that of the untreated fabrics. A positive correlation was clear between crystallite diameter and crystallinity percentage.
No major difference is seen in the inter-plane spacing of untreated and FC-dendrimer-treated fabric, as shown in Table 3. The X-ray diffraction shows that the characteristic peaks of untreated and FC-dendrimer-treated fabric are almost the same. Thus, the cotton fibre cellulose did not produce any remarkable changes after FC-dendrimer incorporation.
Energy-dispersive X-ray spectroscopy (EDX) Analysis
Table 4
Weight % of untreated and treated samples of EDX spectra.
Elements
|
Untreated
fabric
|
60 g/L treated
fabric (Wt.%)
|
70 g/L treated fabric (Wt.%)
|
80 g/L treated fabric (Wt.%)
|
90 g/L treated
fabric (Wt.%)
|
100 g/L treated
fabric (Wt.%)
|
C
|
49.85
|
52.15
|
53.17
|
53.53
|
55.23
|
56.08
|
N
|
00
|
0.20
|
0.27
|
0.38
|
0.57
|
1.63
|
O
|
50.15
|
47.53
|
45.97
|
45.14
|
43.09
|
41.97
|
F
|
00
|
0.12
|
0.33
|
0.60
|
0.82
|
1.43
|
The EDX photograph of untreated fabric and that of FC-dendrimer treated fabrics is shown in Fig. 6. The weight percentages of carbon atoms were 49.85, 52.15, 53.44, 53.91, 55.80, 56.08% in untreated cotton for 60 g/L, 70 g/L, 80 g/L, 90 g/L and 100 g/L FC-dendrimer-treated cotton fabrics, respectively, are listed in Table 4. The weight percentages of oxygen atoms were 50.15, 47.53, 45.97, 45.14, 43.09, and 41.97% in untreated cotton, for 60 g/L, 70 g/L, 80 g/L, 90 g/L and 100g/L in FC-treated cotton fabrics, respectively. The weight percentages of oxygen atoms in FC-dendrimer-treated fabric were less than that in untreated fabric. Fewer oxygen peaks in FC-dendrimer-treated fabric indicate that few hydroxyl groups (OH), which attract water molecules¸ were present. But the weight percentages of carbon atoms were greater in the treated fabric. The greater weight for carbon peaks in FC-dendrimer-treated fabric implies that the number of hydrocarbon groups has increased. Hydrophobicity increases with the increased concentration of fluorocarbon polymer.
Scanning electron microscopy (SEM) study
The surfaces of both the treated and untreated fabrics were studied using a scanning electron microscope. The untreated fabric has a smooth surface, as shown in Fig. 7(a). The treated fabrics had rough and uneven surfaces, as shown in Fig. 7 (b, c, d, e, f) compared to untreated fabric. Granular material was visible in Fig. 7e. That gave the treated fabric its uneven surface and provided evidence that the water repellent agent was successfully attached to the untreated fabric surface. After FC-dendrimer treatment, the surface texture of the cotton fabric became similar to that of non-wettable fabrics. Among the samples, the uneven appearance of the surface of those treated with 90 g/L and 100g/L concentrations of FC-dendrimer treatment was most prominent. This result is similar to the outcome of Jeyasubramanian et al. (Jeyasubramanian et al. 2016).
Thermal analysis
Table 5
TGA and DTA thermograph data of treated and untreated fabrics.
Observation
|
Weight loss %
at 100℃
|
Nature of
DTA peak
|
DTA 1st Peak Temp. (℃)
|
Weight loss % at DTA 1st Peak Temp. (℃)
|
DTA 2nd Peak Temp. (℃)
|
Char residue at 600 ℃, %
|
Untreated fabric
|
6
|
Exothermic
|
377
|
82.4
|
478
|
2.6
|
60 g/L FC-dendrimer
|
5
|
Exothermic
|
379
|
89.5
|
504
|
2.3
|
70 g/L FC-dendrimer
|
5
|
Exothermic
|
376
|
82.7
|
506
|
1.5
|
80 g/L FC-dendrimer
|
3
|
Exothermic
|
380
|
82.6
|
503
|
1.9
|
90 g/L FC-dendrimer
|
4
|
Exothermic
|
382
|
83.2
|
497
|
2.6
|
100 g/L FC-dendrimer
|
6
|
Exothermic
|
382
|
75.1
|
495
|
3.2
|
Thermal behaviour of untreated fabric and FC-dendrimer-treated fabric were evaluated by the study of TGA and DTA thermograms. The weight loss percentage, DTA peak temperature and char residue percentage are shown in Table 5. The TGA thermogram represents the weight loss percentage of the specimen and shows three stages of thermal degradation. In the first stage, weight loss occurred, in the untreated 60, 70, 80, 90 and 100 g/L FC-dendrimer treated fabrics, of 6, 5, 5, 3, 4 and 6%, respectively, at 100°C due to loss of moisture, low molecular weight solvent and expulsion of gas. Major weight losses were observed. In the second stage, at DTA 1st peak temperature, as shown in Table 5. The DTA 1st peak temperatures of the untreated fabric, 60, 70, 80, 90 and 100 g/L FC-dendrimer-treated fabrics were 377, 379, 376, 380, 382, 382℃, respectively. A more-pronounced degradation occurred at this temperature due to the breakdown of glycosidic linkages and hydrogen bonds, leading to the formation of organic compounds. The final-stage residual char is obtained at DTA 2nd peak temperature (Table 5). From Table 5, the DTA peak temperature or decomposition temperature of FC-dendrimer treated fabrics was greater than in untreated fabrics. As a result, the thermal stability of FC-dendrimer treated fabric has been improved. The char residue of 100 g/l FC-dendrimer-treated cloth was higher than that of untreated fabric. In contrast, the char residue of 90 g/l FC-dendrimer treated fabric is similar to that of untreated fabric. On the other hand, char residue rates of 60, 70, and 80 g/L FC-dendrimer-treated fabrics are slightly lower than untreated cotton fabric. The use of polysiloxane, which might have catalyzed cellulose decomposition and resulted in decreased residue after degradation (Flynn 2002). As the add-on percentage was higher with the increase of concentration of FC-dendrimer, this might be the cause of increased residual char % at 100 g/L FC-dendrimer.
Spray test results
Table 6
Standard Spray test rating chart according to AATCC-22 method (Khoddami et al. 2015).
AATCC-22
Standard rating
|
Note
|
AATCC 100
|
100: No sticking or wetting of upper surface
|
AATCC 90
|
90: Slight random sticking or wetting of upper surface
|
AATCC 80
|
80: Wetting of upper surface at spray points
|
AATCC 70
|
70: Partial wetting of whole of upper surface
|
AATCC 50
|
50: Complete wetting of whole surface
|
00
|
0: Complete wetting of whole upper and lower surface
|
Table 7
Spray test readings of FC-dendrimer resin treated fabric.
Observation
|
Spray Test
Readings
(AATCC-22)
|
After five times laundering
(AATCC-22)
|
60 g/L FC-dendrimer treated
|
80
|
80
|
70 g/L FC-dendrimer treated
|
90
|
90
|
80 g/L FC-dendrimer treated
|
90
|
90
|
90 g/L FC-dendrimer treated
|
100
|
100
|
100 g/L FC-dendrimer treated
|
100
|
100
|
Table 7 shows spray-test results for FC-dendrimer-treated fabric. The spray test readings, according to AATCC-22, of 60, 70, 80, 90 and 100 g/L FC-dendrimer-treated samples were 80, 90, 90, 100 and 100, respectively. Standard spray test ratings, according to the AATCC -22 method, are shown in Table 6. According to the rating chart, 90 g/L and 100g/L show the highest rating. This rating implies that there was “No sticking or wetting of the upper surface”. When the concentrations of FC-dendrimer were 90 g/L and 100 g/L, the weight gain percentage was maximized. As a result, the thickness of the treated fabric also increased. So, the treated fabric showed excellent water resistance performance.
Again, at 70 g/L and 80 g/L, the treated sample had a rating of “90’’ meaning “Slight random sticking or wetting”. After five launderings, the spray rating value for all five samples remained unchanged. Repellent finishes achieve repellence because they reduce the free energy on the fibres’ surface. A drop of liquid will spread if the adhesive interactions, between the fibres and the liquid droplets, are greater than the cohesive internal interactions within the liquid. A drop of liquid will not spread, if the adhesive interactions between the fibres and the liquid droplets, are lower than the internal cohesive internal interactions within the liquid. Surfaces that exhibit low interaction with liquids “low-surface energy” surfaces (Schindler and Hauser 2004).
Wash durability
After five launderings, the spray rating value for all five samples remained unchanged.
Water contact angle of the samples
Contact angle measurement is the best method to use to evaluate the water repellence of a hydrophobic surface. The static contact angle is the angle between a liquid and the surface created when the liquid contacts the surface. If the water contact angle is 0\(\le \theta \le 90^\circ\), the surface is defined as “hydrophilic”. If the water contact angle is 90\(\le \theta \le 180^\circ\), the surface is defined as “hydrophobic”. Water repellency increases when cotton fabric with low surface energy is used.
Water contact angle indicates whether a surface is hydrophilic or hydrophobic because it measures how much spread a drop of liquid will achieve on the surface. The surface will become more hydrophilic if oxidizing agents or ion-able groups are introduced on the cotton surface. As a result, a water droplet will spread across the surface more easily, and the water contact angle will become smaller. On the other hand, if hydrocarbons are introduced on the surface, the surface will become more hydrophobic, and the water contact angle will increase. Therefore, to measure the water contact angle, a droplet of water is placed on the surface. The height and width of the water’s spread are then recorded to calculate the angle.
The 100 g/L and 90 g/L FC-dendrimer treated cotton fabric provided excellent water repellence: its water contact angle measured between 154\(^\circ\) and 144\(^\circ\), as shown in Fig. 8 (e, f). 60 g/L, 70 g/L and 80 g/L FC-dendrimer-treated cotton fabrics exhibited water contact angles of 124\(^\circ\), 122\(^\circ\) and 136\(^\circ\), respectively, as shown in Fig. 8 (b, c, d).
Drop test results
This study used 100 g/L FC-dendrimer resin plus 15 g/L blocked polyisocyanate and 10 g/L polysiloxane compound to prepare the sample. A coloured water droplet and paraffin oil spread easily on an untreated fabric surface, as shown in Figs. 9(a) & 5(b), respectively. On the other hand, coloured water droplets and paraffin oil did not spread on the FC-dendrimer treated fabric surface in Fig. 9(c). The spherical shape of the water and oil droplets is shown in Fig. 9(c). Thus, FC dendrimer-treated cotton fabrics are water and oil-repellent.
Hydrostatic pressure test result
Table 8
hydrostatic pressure test result.
Observation
|
Hydrostatic
Pressure (mbar)
|
Untreated fabric
|
140±1.22
|
60 g/L FC treated fabric
|
158±2.83
|
70 g/L FC treated fabric
|
162±2.00
|
80 g/L FC treated fabric
|
168±2.55
|
90 g/L FC treated fabric
|
175±1.22
|
100 g/L FC treated fabric
|
180±1.87
|
Hydrostatic pressure means the pressure needed for water to penetrate a fabric. Hydrostatic pressure increased after FC-dendrimer coating, compared to that of untreated fabric.
Table 8 shows this increase. Hydrostatic pressure increases gradually with the increase of coating because the FC-dendrimer polymer coating on the fabric becomes denser as the chemicals concentration increases. A denser coating makes the fibre more water-repellent. The highest hydrostatic pressure (180 mbar) and lowest hydrostatic pressure (158 mbar) were reached with coatings of 100 g/L, and 60 g/L treated fabrics, respectively. Hydrostatic pressure is directly proportional to the water repellency property. High hydrostatic pressure indicates a high repellent property. So, it can say that 100 g/L FC-dendrimer finished fabric exhibits the highest water repellence.
Oil repellence
The surface tension and density of paraffin oil are 31.5 mN/m and 0.86 kg/dm3, respectively, as shown in Table 1. Kasturiya & Bhargava (Kasturiya and Bhargava 2003) found that the critical surface tension for FC-dendrimer polymer-coated surfaces is 6 mN/m - 28 mN/m. Yet, for bleached cotton, this critical surface tension is 44 mN/m. When FC-dendrimer polymer is applied to bleached cotton fabric, the surface tension is reduced to 6 mN/m - 28 mN/m. Paraffin oil did not penetrate the FC-dendrimer-treated fabric, as the surface tension of paraffin oil is greater than that of the FC-dendrimer-treated fabric. On the other hand, paraffin oil easily penetrates the bleached cotton fabric since the surface tension of paraffin oil is less than that of the bleached cotton fabric. So, it can say that the 60 g/L, 70 g/L, 80 g/L, 90 g/L and 100 g/L FC-dendrimer treated fabric showed paraffin oil repellence.
The surface tension and density of n-heptane are 19.8 mN/m and 0.69 kg/dm3, respectively. The surface tension of n-heptane is less than that of the other organic oils used in the oil repellence test, as shown in Table 1. N-heptane organic oil can easily wet 60 g/L, 70 g/L, and 80 g/L FC-dendrimer-treated fabric, but not 90 g/L and 100 g/L FC-dendrimer-treated fabric. Therefore, according to the oil repellence test chart, 90 g/L and 100 g/L FC-dendrimer-treated fabric showed an oil repellence rating of 8 (eight) as shown in Table 1. A high value of water contact angle also indicated a high degree of oleophobicity. The water contact angle of 90 and 100g/L FC- dendrimer-treated fabrics are 154° and 144° as in Fig. 8 (e, f).
The surface tension and density of n-octane are 21.4 mN/m and 0.70 kg/dm3, respectively. N-octane organic oil can easily wet 60g/L and 70 g/L FC-dendrimer-treated fabric but not 80 g/L FC-dendrimer-treated fabric. So, 80 g/L FC-dendrimer-treated fabric achieved an oil repellence rating of 7 (seven), according to Table 1.
N-decane organic oil cannot wet the 60 g/L and 70 g/L FC-dendrimer-treated fabric, as the surface tension of n-decane is higher than that of n-octane. So, 60 g/L and 70 g/L FC-dendrimer-treated fabric achieved an oil repellence rating of 6 (six) according to Table 1. The oil repellence ratings of all the FC-dendrimer-treated samples are illustrated in Fig. 10.
Oil-water separation
Oil-water separation becomes a crucial issue due to considerable oily wastewater from agricultural and industrial activities. On the other hand, improper disposal of used motor oil, oil spills, or leaks from ships or tankers have considerably contaminated watercourses and our food chain. (Wang et al. 2016; Cao and Cheng 2018; Yuan et al. 2018; Baig et al. 2019).
All concentrated FC-dendrimer-treated fabrics exhibited hydrophobic characteristics because the surface tension of water is fixed. On the other hand, FC-dendrimer-treated fabric showed oleophobic and oleophilic characteristics determined by the different surface tensions of the different organic oils tested. For example, n-decane cannot penetrate the 60g/L and 70 g/L FC-dendrimer-treated fabric, but n-octane can do so easily. As a result, a mixture of n-octane and water can be separated by 60 g/L and 70 g/L FC-dendrimer-treated fabric. Similarly, a mixture of n-heptane and water has been separated by 60, 70 and 80 g/L FC-dendrimer-treated fabric. In addition, It may also separate the n-hexane and water mixture using any FC-dendrimer-treated fabric as the surface tension (18.43 mN/m) of n-hexane organic oil is less than that of all the FC-dendrimer-treated fabric.
50 mL water and 50 mL n-hexane were mixed, and used 100 g/L FC-dendrimer-treated fabric for separation. After separation, the collected water remaining was still about 50 mL. The collected oil decreased a little in volume due to the absorbency of cotton and volatilization. The coated cotton would let the oil permeate until saturation in the parts which make contact with it. The FC-dendrimer-treated cotton, however, showed excellent oil-water separation.
The separation efficiency of FC-dendrimer-treated cotton was 97-99%, as calculated according to equation (4). A schematic diagram of oil-water separation is shown in Fig. 11. Materials which can repel water even amidst oily pollutants are very useful in seawater. Thus, as described here, coated fabric with dual functionality, is a promising material for anti-wetting, self-cleaning, support for aquatic floating devices and as a filtration material for rapid, continuous oil-water separation.
Acid resistance
Among the possible applications of acid-resistant fabric are petroleum, chemistry, metallurgy, and electroplating. Workers in these industries need clothing made of such fabric to protect them from the dangerous acids they work with. In the past, clothing was made acid-resistant by coating it with rubber or hydrocarbon resins. These resins created a continuous film on the textile, which closed its empty spaces, stopping the intrusion of acid (Forsberg et al. 2014). Gal’braikh (2005) proved that fluoropolymers effectively resist corrosive solutions, including acid. Wang et al. (2011) and Zhou et al. (2013) used fluorinated polymers, which resisted acid most effectively.
The acid resistance performance of the untreated fabric and 100 g/L FC-dendrimer treated fabrics is shown in Fig. 12. Initially, 100 g/L FC-dendrimer was not affected by an acid droplet Fig. 12a. But the untreated fabric was affected by acid droplets to some extent Fig. 12b. After 30 minutes, the treated fabric washes with water. Colour change had taken place where the acid droplet had landed Fig. 12c. A large area of untreated fabric was burnt Fig. 12d by the acid droplet after 30 minutes.
Self-cleaning `
Water-resistant finishes are chemical additions to clothing that enhance the hydrophobic nature of a fabric’s surface. Completely hydrophobic surfaces also must be self-cleaning. Hydrophobic and self-cleaning attributes are exhibited in many surfaces of nature, such as the wings of butterflies, the leaves of cabbage and lotus, the elephant’s ears and Indian cress. The surface of lotus leaves has protruding nubs, as proven by Scanning Electron Microscopy. Epicuticle wax crystalloid encloses each nub. Due to these crystalloids, lotus leaves clean themselves and have a water contact angle (WCA) of 160. From this model, researchers have created artificial surfaces with water contact angles greater than 90o (Guo et al. 2011; Lin et al. 2011; Li et al. 2014; Xu et al. 2010).
Self-cleaning coatings include: (Yoshida et al. 2006)
- photocatalysis-induced superhydrophilic coatings and
- superhydrophobic coatings.
In super-hydrophilic coatings, the surface is cleaned by the sheeting effect of water. Complex organic substances on the surface are broken down into carbon dioxide and water. Superhydrophobic coatings have air pockets that get trapped between the nano-structured substrate and water droplets. The formation of a composite solid/air/liquid interface leads to an increase in the contact angle (CA) of liquid droplets. Increased contact angle leads to de-wetting of the surface. Then the droplet rolls off easily, taking away dirt and pollutants with it.
Figure 13(a) shows that methylene blue dye powder spread widely on the untreated fabric surface due to the capillary effects of cotton fibers. The coated cotton surface has extremely little adhesion to methylene blue dye powder. However, water droplets quickly and easily removed dirt-like methylene blue dye powder on the superhydrophobic cotton surface. Thus, the surface in Figure 13(b-f) is clean and dry. Among the treated samples, 80 g/L, 90 g/L and 100 g/L FC-treated samples showed better self-cleaning performance than the 60 g/L and 70 g/L FC-treated samples.
Flame retardant property
Figure 14 illustrates that burning times for untreated, 60, 70, 80, 90, and 100 g/L treated fabrics were 10.5, 10.94, 11.44, 13.73, 14.3 and 14.6 seconds, respectively. Burning times of all the FC-dendrimer-treated samples were greater than that of the untreated samples. Burning time increased with an increase in the FC-dendrimer concentration. Burning time mainly depends on the amount of polymer loading on the sample and the amount of oxygen. Less oxygen in the sample increases the burning time. EDS results show that oxygen in untreated, 60, 70, 80, 90, and 100 g/L treated fabrics were 50.15, 47.53, 45.97, 45.14, 43.09, 41.97, respectively, as shown in Table 4. EDX results indicate that the oxygen level of untreated fabric was greater than that of the treated fabric. These results also revealed that the weight percentage of oxygen decreased with increasing concentrations of FC-dendrimer polymer solution as shown in Table 4.
The limiting oxygen index (LOI) is the minimum oxygen concentration needed to support the flaming combustion in a mixture of oxygen and nitrogen. The limiting oxygen index (LOI) of untreated cotton fabric was 17.8, and the treated fabric was 18. Thus, the flame retardant property of FC-dendrimer-treated fabric remains almost unchanged.
UV Protection Factor (UPF)
The United States Environmental Protection Agency has stated that 80% of the sun's UV rays reach the Earth, damaging human skin (The United States Environmental Protection Agency 2004), even in cold climates (Skin Cancer Foundation 2015). For this reason, it is essential to wear UV protective garments on cloudy or rainy days and sunny days. Therefore, there is a strong demand for UV-resistant garments all over the world. There are three kinds of UV light:
- UV-A (315-400 nm),
- UV-B (280-315 nm) and
- UV-C (100-290nm).
The ozone layer absorbs UV-C radiation. UV-A and UV-B radiation reach the earth’s surface. These are the ones that can cause serious health problems. Ultraviolet radiation (UV-R) on earth is comprised of UV-A and UV-B rays. Its wavelength range is 280-400 nm.
Clothing serves as a link window between the outside environment and the human body. It can reflect, absorb, or scatter solar waves. Thus, ordinary clothing is usually not enough to protect the human body from the harmful effects of UV radiation. For this reason, UV-resistant finishing on textiles is necessary.
Table 9
Ultra-violet Protection Factor (UPF) of untreated and FC-dendrimer treated fabrics.
Observation
|
Mean
UV-A transmission
|
UPF rating of UV-A
|
Mean
UV-B transmission
|
UPF rating of UV-B
|
Mean UV-R transmission
|
UPF rating
of UV-R
|
60 g/L
|
0.657
|
2.16
|
0.113
|
4.00
|
0.476
|
2.84
|
70 g/L
|
0.426
|
3.16
|
0.111
|
4.11
|
0.315
|
3.25
|
80 g/L
|
0.415
|
3.21
|
0.109
|
4.23
|
0.314
|
3.49
|
90 g/L
|
0.278
|
4.22
|
0.089
|
4.95
|
0.221
|
3.66
|
100 g/L
|
0.275
|
4.58
|
0.081
|
5.42
|
0.213
|
4.42
|
# Mean UV-R transmission value of untreated sample was 2.792; and UPF value of untreated sample was 0.25. |
Table 9 illustrates that UPF value gradually increased with increasing FC-dendrimer concentration. The relationship between UPF rating and transmittance value is inversely proportional. The UPF value of the 100 g/L FC-dendrimer-treated samples was 4.42 for UV-R, nine times greater than that of the untreated sample. Pande and Crooks (Pande and Crooks 2011) identified the absorbance peak at 280 to 285 nm which is caused by the dendrimer structure. A dendrimer is a key component for maximizing the ultra-violet protection capacity of FC-dendrimer-treated clothing.
Antimicrobial activity
Clothing that fights germs is better for human health. Sometimes, as in a medical environment, it is essential. If clothing is water-, oil- and dirt-repellant and UV-protective and antimicrobial, this is almost ideal in many applications (Attia et al. 2017).
Antimicrobial clothing materials can be active or passive. Passive materials do not contain bioactive substances. Only the surface structure of the passive material can resist microbial contamination. Examples include “the lotus effect” and the micro-domain-structured surface. The key is to make it impossible for microbial cells to adhere to the fibre’s surfaces. Active antimicrobial clothing contains bioactive substances which kill microbes (Russell and Chopra 1996; Beumer et al. 2000).
Recently, modified dendrimers have been proposed to develop antimicrobial properties for applications to textiles. Ghosh et al. (2010) observed effective antimicrobial activities of the modified-dendrimer treated‐fabric against Staphylococcus aureus (S. aureus).
Clear microbial inhibition zones were not found for treated fabrics in Fig. 15 (b-f). However, bacterial population growth seems to be less on the FC-dendrimer-treated samples in Fig. 15(b-f) than on the untreated sample in Fig. 15(a). Among the treated samples, 100 g/L FC-dendrimer treated fabric (Fig. 15(f)) showed the lowest bacterial population growth. The bacterial population was assessed by visual inspection. Around the untreated sample, the area is more ambiguous than the treated fabric. More ambiguity indicates a higher bacterial population.
FC-dendrimer polymer has no active antimicrobial properties. But it can act as a passive antimicrobial agent, due to converting fabric surfaces to super-hydrophobic surfaces. Hydrophobic and super-hydrophobic fabrics resist bacterial adherence by making it a slippery surface like that of lotus leaves.
In this study, RUCO STAR EEE 6 was used, containing dendrimers and FC resin. It is assumed that the amino group (NH2) in dendrimer is the functional group responsible for its antibacterial activity. After FC-dendrimer treatment, 100 g/L FC-dendrimer-treated samples exhibited the highest nitrogen level (1.63%), as found by EDS analysis.
GSM and thickness measurement
Table 10
Thickness and GSM of treated and untreated fabric.
Observation
|
Thickness (mm)
|
Thickness
Increase (%)
|
GSM (g/m2)
|
GSM
Increase (%)
|
Untreated
|
0.480±.024
|
-
|
180±3.39
|
-
|
60 g/L FC-dendrimer treated
|
0.502±.012
|
4.58
|
185±3.42
|
2.70
|
70 g/L FC-dendrimer treated
|
0.506±.007
|
5.83
|
187±2.92
|
3.74
|
80 g/L FC-dendrimer treated
|
0.508±.008
|
7.50
|
188±2.92
|
4.25
|
90 g/L FC-dendrimer treated
|
0.522±.009
|
8.75
|
190±2.83
|
5.26
|
100 g/L FC-dendrimer treated
|
0.524±.006
|
9.16
|
191±2.59
|
5.75
|
After FC-dendrimer treatment, GSM and thickness of the treated fabrics increased markedly compared to that of the untreated fabric (Table 10). The FC-dendrimer resin closed all the pores in the fabric, creating a chemical coating. That was the reason behind the thickness and weight increases of the fabric. Both GSM and thickness gradually increased with increased FC-dendrimer resin concentration.
Bursting strength measurement
Table 11
Bursting strength test result.
Observation
|
Bursting strength (Kpa)
|
Untreated fabric
|
176 ± 2.39
|
60 g/L FC treated fabric
|
180 ± 1.92
|
70 g/L FC treated fabric
|
183 ± 1.92
|
80 g/L FC treated fabric
|
186 ± 2.07
|
90 g/L FC treated fabric
|
189 ± 1.64
|
100 g/L FC treated fabric
|
188 ± 1.58
|
Bursting strength is the amount of pressure that ruptures the fabric. The increase or decrease in bursting strength is mainly a function of the smoothness or roughness of the treated fabric’s surface. Generally, a smooth surface increases bursting strength and vice-versa. The SEM image revealed that micro-roughness was developed on fluorocarbon-treated cotton (Fig. 15(b-f)) in comparison to the untreated cotton fabric. Micro-surface roughness increases with the increased water contact angle of the treated fabric. But, visually, FC-dendrimer-treated cotton fabric showed a smooth surface. It is assumed that softening agents, like non-ionic polysiloxane, were the main contributor factors for the treated fabric’s visual smoothness and smooth feel. In the present study, Table 11 shows that the bursting strength of treated fabric increases as the FC-dendrimer concentration increases.
Additionally, the SEM result did not support the present outcome. The true explanation for this is still unclear.
Abrasion resistance measurement
The study aimed to see if the treated fabrics could withstand abrasion. The spray rating remained unchanged after 5,000 rub cycles, according to the results (Table 12). On the other hand, water repellency decreased a little after 10,000 rub cycles. Water spray rating of 60 g/L FC-dendrimer treated fabric was maintained at 4 using the ASTM D4966-98 (1989) standard. After 10,000 rub cycles, 70 g/L FC-dendrimer treated fabric maintains a 4-5 spray rating. 80, 90, 100 g/L FC-dendrimer treated fabrics showed the best abrasion resistance.
Table 12
Spray rating result after abrasion.
Observation
|
Martindale rub cycle
|
Spray rating after abrasion
|
Martindale rub cycle
|
Spray rating after abrasion
|
60 g/l FC-D treated fabric
|
5000
|
5
|
10, 000
|
4
|
70 g/l FC-D treated fabric
|
5000
|
5
|
10,000
|
4-5
|
80 g/l FC-D treated fabric
|
5000
|
5
|
10,000
|
5
|
90 g/l FC-D treated fabric
|
5000
|
5
|
10,000
|
5
|
100 g/l FC-D treated fabric
|
5000
|
5
|
10,000
|
5
|
Thermal conductivity
Thermal conductivity is heat flow through a material. Table 13 illustrates that the least conductivity existed in 100 g/L FC-dendrimer-treated fabric, and maximum conductivity was observed in 60 g/L concentration. The thermal conductivity value decreased as the thickness and GSM of the treated sample gradually increased. As FC-dendrimer concentration increased, the rate of heat transfer decreased. The thermal conductivity rate of 90 g/L and 100 g/L FC-dendrimer-treated fabric was decreased to 40% and 54%, respectively, due to their greater thickness. Moreover, it is assumed that changing the surface morphology of the treated fabric also created barriers to thermal conductivity. SEM study revealed that the FC-dendrimer polymer filled the pores of the untreated fabrics and deposited small amounts of granular material on the surface of the treated fabric, which would reduce thermal conductivity in the treated sample.
Table 13
Thermal conductivity test results and their Chi-Square (2) hypothesis test observation (Degree of freedom: (3-1) =2; Level of significance; 5%).
Observation
|
Thermal conductivity (Cal/cm/s/˚C) \(\times\)10−3
|
Calculated value
|
Tabulated value
|
Comments
|
60 g/L FC-dendrimer treated
|
17.8±0.18
|
2.73
|
5.99
|
Null hypothesis test is accepted
|
70 g/L FC-dendrimer treated
|
16.53±0.34
|
4.46
|
Null hypothesis test is accepted
|
80 g/L FC-dendrimer treated
|
15.63±0.29
|
5.98
|
Null hypothesis test is accepted
|
90 g/L FC-dendrimer treated
|
13.43±0.29
|
10.81
|
Null hypothesis test is rejected
|
100 g/L FC-dendrimer treated
|
10.26±0.21
|
19.46
|
Null hypothesis test is rejected
|
*Thermal conductivity of untreated fabric: 22.3 (Cal/cm/s/˚c) \(\times\)10−3 |
The calculated values for thermal conductivity of 60 g/L, 70 g/L and 80 g/L FC-dendrimer-treated fabric are less than the tabulated values as shown in Table 13, so the null hypothesis is accepted. On the other hand, the calculated values of 90 g/L and 100 g/L FC-dendrimer-treated fabrics are greater than the tabulated values: as a result, the null hypothesis is rejected.
Therefore, thermal conductivity will not be hampered by 60 g/L, 70 g/L and 80 g/L FC-dendrimer treatment. But the comfort properties of the fabric will be significantly and negatively affected by 90 g/L and 100 g/L FC-dendrimer treatment.
Air permeability
Comfort and breathability are closely related to air permeability. The air permeability rate of 60 g/L, 70 g/L, 80 g/L, 90 g/L and 100 g/L FC-dendrimer treated fabric was 829, 818, 790, 750 and 733 m3/m2/h, respectively, as shown in Table 14. The highest air permeability value existed in 60 g/L fabric, and the air permeability of 90 g/L and 100 g/L treated fabrics were 13% and 15% lower, respectively, than that of untreated fabric. As the concentration of FC-dendrimer coating materials increased, the pickup percentage gradually increased and, as a direct result, the air permeability value declined.
Cross-linking networks may form on the water-repellent finish. The FC-dendrimer treatment results in blocking some pores, which may be responsible for less air permeability. These are some of the factors that may create less air permeability.
Table 14
Air permeability test results and their Chi-Square (2) hypothesis test observation (Degree of freedom: 3-1 = 2; and Level of significance; 5%).
Observation
|
Mean value of Air Permeability rate in (m3/m2/hour)
|
Chi-square
calculated value
|
Chi-square Tabulated value
|
Comments
|
60 g/L FC-dendrimer
treated fabric
|
829±1.92
|
3.29
|
5.99
|
Null hypothesis test is accepted
|
70 g/L FC-dendrimer
treated fabric
|
818±2.07
|
5.97
|
Null hypothesis test is accepted
|
80 g/L FC-dendrimer
treated fabric
|
818±2.07
|
16.78
|
Null hypothesis test is rejected
|
90 g/L FC-dendrimer treated fabric
|
749±1.58
|
42.46
|
Null hypothesis test is rejected
|
100 g/L FC-dendrimer
treated fabric
|
790±2.59
|
56.56
|
Null hypothesis test is rejected
|
Air permeability of untreated fabric: 860 (m3/m2/hour) |
The critical chi-square value is evaluated at a 5% level of significance with two degrees of freedom. For each sample, we took three observations. The calculated values for 60 g/L and 70 g/L FC-dendrimer-treated fabrics are less than the tabulated values as shown in Table 14, so the null hypothesis is accepted. On the other hand, the calculated value for 80 g/L, 90 g/L and 100 g/L is greater than the tabulated value, as shown in Table 14, so the null hypothesis is rejected. The 80 g/L, 90 g/L and 100 g/L FC-dendrimer-treated fabric observation did not achieve a sufficient value for accepting the null hypothesis, but the 60 g/L and 70 g/L FC-dendrimer-treated fabric observation did.
Thus, we conclude that 60 g/L and 70 g/L FC-dendrimer treatment will not hamper the air permeability or comfort of the fabric. But this will not hold at higher levels of FC-dendrimer concentration.
Water vapour permeability
Clothing should be able to let water vapour pass through it. Otherwise, heat accumulates in the body as humid water vapour is impacted between clothing and the body. Similarly, perspiration should pass through clothing. Lighter fabrics (less mass per square meter and thickness) permit the easy passage of water vapour through the fabrics.
The water vapour permeability rate decreased with the increased concentration of FC-dendrimer, as shown in Table 15. The water vapour permeability of 60 g/L, 70 g/L, 80 g/L, 90 g/L, and 100 g/L FC-dendrimer-treated fabrics were 1249, 1240, 1231, 1221 and 1212 gm/m2/day, respectively.
Table 15
The results of water vapour permeability readings with variation of C6-FC-dendrimers.
Observation
|
After 01 hour in gm/m2
|
After 02 hour in gm/m2
|
After 03 hour in gm/m2
|
After 04 hour in gm/m2
|
After 24 hour
gm/m2
|
60 g/L FC-dendrimer treated fabric
|
41
|
85
|
142
|
222
|
1249
|
70 g/L FC-dendrimer treated fabric
|
38
|
83
|
139
|
219
|
1240
|
80 g/L FC-dendrimer treated fabric
|
37
|
80
|
137
|
217
|
1231
|
90 g/L FC-dendrimer treated fabric
|
35
|
78
|
135
|
213
|
1221
|
100 g/L FC-dendrimer treated fabric
|
32
|
75
|
133
|
207
|
1212
|
*Water vapour permeability of untreated fabric - 1288 gm/ m2/day |
Table 16
Chi-Square (2) hypothesis test observation in terms of water vapour permeability value of treated fabric (Degree of freedom: (3-1) = 2; Level of significance, 5%).
Observation
|
Calculated
value
|
Tabulated
value
|
Comments
|
60 g/L FC-dendrimer treated fabric
|
3.6
|
5.99
|
Null hypothesis
test is accepted
|
70 g/L FC-dendrimer treated fabric
|
5.51
|
Null hypothesis
test is accepted
|
80 g/L FC-dendrimer treated fabric
|
7.65
|
Null hypothesis
test is rejected
|
90 g/L FC-dendrimer treated fabric
|
10.56
|
Null hypothesis
test is rejected
|
100 g/L FC-dendrimer treated fabric
|
13.69
|
Null hypothesis
test is rejected
|
Water vapour permeability of untreated fabric: 1288 gm/ m2/day |
The calculated values of 60 g/L and 70 g/L FC-dendrimer-treated fabrics are less than the tabulated value, as shown in Table 16, so the null hypothesis is accepted. On the other hand, the calculated values of 80 g/L, 90 g/L and 100 g/L FC-dendrimer-treated fabrics are greater than the tabulated values: as a result, the null hypothesis is rejected.
It may determine that FC-dendrimer treatment at 60 g/L and 70 g/L does not affect on water vapour permeability or comfort qualities. However, treatment with 80, 90, and 100 g/L FC-dendrimer significantly reduces comfort qualities.